Solar Rooftop ROI Calculator

Size your system to match annual consumption. Take your average monthly bill, divide by your tariff to get monthly units (kWh), multiply by 12.

Then divide by your local annual yield per kW — 1,400-1,600 kWh/kW for most of the country, lower in coastal/cloudy areas, higher in arid Rajasthan/Gujarat.

For a household with a ₹3,500/month bill at ₹8/kWh, annual consumption is 5,250 kWh — a 3.5 kW system at 1,500 kWh/kW yields 5,250 kWh, a perfect match. Going under-sized still delivers savings, but you don't get full grid-import offset. Going over-sized loses the surplus because most net-metering policies don't pay cash for net-positive units.

Typical payback is 3-5 years for a well-sized residential rooftop solar system after the PM Surya Ghar subsidy.

A 3 kW system at ₹55,000/kW costs ₹1.65 lakh gross, ₹87,000 net after the ₹78,000 subsidy. At ₹8/kWh and 1,500 kWh/kW annual yield, annual savings are around ₹36,000 — payback in about 2.4 years.

Higher tariffs (₹9-12/kWh in Maharashtra, Tamil Nadu, Delhi commercial slabs) push payback below 2 years. Lower tariffs (₹5-6/kWh in subsidised slabs) extend payback to 4-5 years. After payback, the next 20+ years of generation are essentially free electricity for the panel's 25-year warranted life.

Net metering is a billing mechanism where your rooftop solar feeds excess generation into the grid during the day, and you draw from the grid at night or on cloudy days. Your meter records both directions, and you are billed only on the net consumption.

Most states (Maharashtra, Karnataka, Tamil Nadu, Gujarat) use 1:1 net metering — each exported unit offsets one imported unit at the same tariff. Some states have moved to gross metering, where exported units are paid at a separate feed-in tariff (typically 80-90% of retail).

Always check your state DISCOM's current policy before sizing the system — gross metering reduces returns on over-sized systems because surplus units don't earn full retail rate.

Yes, but at reduced output. Modern mono PERC bifacial panels generate 10-25% of rated capacity even on overcast days because diffused light still reaches the cells.

Monsoon months (June-September) typically produce 40-60% of peak summer output. The annual yield figures of 1,400-1,600 kWh/kW already factor in seasonal variation, dust, shading and cloudy days — this is the realistic 365-day average.

Rain actually helps by washing dust off the panels, improving subsequent generation. Panels also work fine in winter; cold temperatures slightly improve efficiency (silicon performs better at lower temperatures).